1. Field of Invention
The present invention relates to a method of fabricating a semiconductor device, and to a semiconductor element composite, an electro-optical apparatus, and an electronic system, each including the semiconductor device fabricated by the method.
2. Description of Related Art
The related art includes techniques of forming a semiconductor element on a substrate composed of a different material. For example, a surface-emitting laser (VCSEL), photodiode (PD), or high electron mobility transistor (HEMT) composed of gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), or the like is disposed on a silicon semiconductor substrate, and in a liquid crystal display (LCD), silicon microtransistors, instead of thin-film transistors (TFTs), for the individual pixels are bonded to a glass substrate.
One example of the integrated circuit provided with semiconductors composed of different materials is an optoelectronic integrated circuit (OEIC). The optoelectronic integrated circuit includes an optical input/output device, and although signal processing is performed using electrical signals in the integrated circuit, input/output with the outside of the integrated circuit is performed using optical signals.
In computers, with the miniaturization of the internal structure of the integrated circuit, the operating speed (operation clock) in the CPU is improving year by year. However, in the related art, the signal transmission speed in the bus is almost reaching the limit, which is a bottleneck in the computer processing speed. If signal transmission in the bus is performed using optical signals, it becomes possible to remarkably increase the limit of the computer processing speed. In order to achieve this, small photodetectors/light-emitting elements must be built into the integrated circuit composed of silicon.
However, silicon cannot emit light because it is an indirect gap semiconductor. Therefore, silicon and a semiconductor light-emitting element composed of a material that is different from silicon must be combined to construct an integrated circuit.
One example of a potential semiconductor light-emitting element is a surface-emitting laser (VCSEL) composed of a compound semiconductor, such as gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs). However, since such a surface-emitting laser has poor lattice matching with silicon, it is extremely difficult to form the surface-emitting laser directly on a silicon integrated circuit by a semiconductor process, such as epitaxy.
The surface-emitting laser is usually formed on a gallium arsenide substrate. Accordingly, the related art includes a method in which the surface-emitting laser formed on the substrate is formed into a chip, and the chip is mechanically mounted on a silicon integrated circuit board, thereby integrating an electrical signal transmission circuit and an optical signal transmission circuit with each other.